Abstract：
CTC1-STN1-TEN1 (CST) is a single-stranded DNA binding protein vital for telomere length maintenance with additional genome-wide roles in DNA replication and repair. While CST was previously shown to function in double-strand break repair and promote replication restart, it is currently unclear whether it has specialized roles in other DNA repair pathways. Proper and efficient repair of DNA is critical to protecting genome integrity. Telomeres and other G-rich regions are strongly predisposed to oxidative DNA damage in the form of 8-oxoguanines, which are typically repaired by the base-excision repair (BER) pathway. Moreover, recent studies suggest that CST functions in the repair of oxidative DNA lesions. Therefore, we tested whether CST interacts with and regulates BER protein activity. Here, we show that CST robustly stimulates proteins involved in BER, including OGG1, Pol β, APE1, and LIGI, on both telomeric and non-telomeric DNA substrates. Biochemical reconstitution of the pathway indicates that CST stimulates BER. Finally, knockout of STN1 or CTC1 leads to increased levels of 8-oxoguanine, suggesting defective BER in the absence of CST. Combined, our results define an undiscovered function of CST in BER, where it acts as a stimulatory factor to promote efficient genome-wide oxidative repair.
摘要：
CTC1-STN1-TEN1（CST）是一种单链DNA结合蛋白，对于端粒长度维持至关重要，在DNA复制和修复中具有其他全基因组作用。虽然CST以前被证明在双链断裂修复中起作用并促进复制重启，目前尚不清楚它是否在其他DNA修复途径中具有专门作用.正确和有效的DNA修复对于保护基因组完整性至关重要。端粒和其他富含G的区域强烈倾向于以8-氧胍的形式氧化DNA损伤，通常通过碱基切除修复（BER）途径修复。此外，最近的研究表明CST在氧化性DNA损伤的修复中起作用。因此,我们测试了CST是否与BER蛋白相互作用并调节其活性。这里,我们表明CST强烈刺激参与BER的蛋白质，包括OGG1，Polβ，APE1和LIGI,在端粒和非端粒DNA底物上。该途径的生化重建表明CST刺激BER。最后,敲除STN1或CTC1导致8-氧鸟嘌呤水平升高，表明在没有CST的情况下有缺陷的BER。合并,我们的结果定义了BER中CST的一个未被发现的函数，它作为刺激因子促进有效的全基因组氧化修复。
